  function equal(actual, expected, description) {
    it(description, function() {
      expect(actual).toBe(expected);
    });
  }
  function deepEqual(actual, expected, description) {
    it(description, function() {
      expect(actual).toEqual(expected);
    });
  }
  function strictEqual(actual, expected, description) {
    it(description, function() {
      expect(actual).toBe(expected);
    });
  }  
  function ok(actual, description) {
    expect(actual).toBe(true);
  }  
  describe('first', function() {
    equal(_.first([1,2,3]), 1, 'can pull out the first element of an array');
    equal(_([1, 2, 3]).first(), 1, 'can perform OO-style "first()"');
    deepEqual(_.first([1, 2, 3], 0), [], 'can pass an index to first');
    deepEqual(_.first([1, 2, 3], 2), [1, 2], 'can pass an index to first');
    deepEqual(_.first([1, 2, 3], 5), [1, 2, 3], 'can pass an index to first');
    var result = (function(){ return _.first(arguments); })(4, 3, 2, 1);
    equal(result, 4, 'works on an arguments object.');
    result = _.map([[1,2,3],[1,2,3]], _.first);
    deepEqual(result, [1, 1], 'works well with _.map');
    result = (function() { return _.take([1,2,3], 2); })();
    deepEqual(result, [1, 2], 'aliased as take');

    equal(_.first(null), undefined, 'handles nulls');
    strictEqual(_.first([1, 2, 3], -1).length, 0);
  });

  describe('rest', function() {
    var numbers = [1, 2, 3, 4];
    deepEqual(_.rest(numbers), [2, 3, 4], 'working rest()');
    deepEqual(_.rest(numbers, 0), [1, 2, 3, 4], 'working rest(0)');
    deepEqual(_.rest(numbers, 2), [3, 4], 'rest can take an index');
    var result = (function(){ return _(arguments).tail(); })(1, 2, 3, 4);
    deepEqual(result, [2, 3, 4], 'aliased as tail and works on arguments object');
    result = _.map([[1,2,3],[1,2,3]], _.rest);
    deepEqual(_.flatten(result), [2, 3, 2, 3], 'works well with _.map');
    result = (function(){ return _(arguments).drop(); })(1, 2, 3, 4);
    deepEqual(result, [2, 3, 4], 'aliased as drop and works on arguments object');
  });

  describe('initial', function() {
    deepEqual(_.initial([1, 2, 3, 4, 5]), [1, 2, 3, 4], 'working initial()');
    deepEqual(_.initial([1, 2, 3, 4], 2), [1, 2], 'initial can take an index');
//    deepEqual(_.initial([1, 2, 3, 4], 6), [], 'initial can take a large index');
    var result = (function(){ return _(arguments).initial(); })(1, 2, 3, 4);
    deepEqual(result, [1, 2, 3], 'initial works on arguments object');
    result = _.map([[1,2,3],[1,2,3]], _.initial);
    deepEqual(_.flatten(result), [1, 2, 1, 2], 'initial works with _.map');
  });

  describe('last', function() {
    equal(_.last([1,2,3]), 3, 'can pull out the last element of an array');
    deepEqual(_.last([1, 2, 3], 0), [], 'can pass an index to last');
    deepEqual(_.last([1, 2, 3], 2), [2, 3], 'can pass an index to last');
    deepEqual(_.last([1, 2, 3], 5), [1, 2, 3], 'can pass an index to last');
    var result = (function(){ return _(arguments).last(); })(1, 2, 3, 4);
    equal(result, 4, 'works on an arguments object');
    result = _.map([[1,2,3],[1,2,3]], _.last);
    deepEqual(result, [3, 3], 'works well with _.map');

    equal(_.last(null), undefined, 'handles nulls');
    strictEqual(_.last([1, 2, 3], -1).length, 0);
  });

  describe('compact', function() {
    equal(_.compact([0, 1, false, 2, false, 3]).length, 3, 'can trim out all falsy values');
    var result = (function(){ return _.compact(arguments).length; })(0, 1, false, 2, false, 3);
    equal(result, 3, 'works on an arguments object');
  });

  describe('flatten', function() {
    var list = [1, [2], [3, [[[4]]]]];
    deepEqual(_.flatten(list), [1,2,3,4], 'can flatten nested arrays');
    deepEqual(_.flatten(list, true), [1,2,3,[[[4]]]], 'can shallowly flatten nested arrays');
    var result = (function(){ return _.flatten(arguments); })(1, [2], [3, [[[4]]]]);
    deepEqual(result, [1,2,3,4], 'works on an arguments object');
    list = [[1], [2], [3], [[4]]];
    deepEqual(_.flatten(list, true), [1, 2, 3, [4]], 'can shallowly flatten arrays containing only other arrays');
  });

  describe('without', function() {
    var list = [1, 2, 1, 0, 3, 1, 4];
    deepEqual(_.without(list, 0, 1), [2, 3, 4], 'can remove all instances of an object');
    var result = (function(){ return _.without(arguments, 0, 1); })(1, 2, 1, 0, 3, 1, 4);
    deepEqual(result, [2, 3, 4], 'works on an arguments object');

    list = [{one : 1}, {two : 2}];
    ok(_.without(list, {one : 1}).length == 2, 'uses real object identity for comparisons.');
    ok(_.without(list, list[0]).length == 1, 'ditto.');
  });

  describe('uniq', function() {
    var list = [1, 2, 1, 3, 1, 4];
    deepEqual(_.uniq(list), [1, 2, 3, 4], 'can find the unique values of an unsorted array');

    list = [1, 1, 1, 2, 2, 3];
    deepEqual(_.uniq(list, true), [1, 2, 3], 'can find the unique values of a sorted array faster');

    list = [{name:'moe'}, {name:'curly'}, {name:'larry'}, {name:'curly'}];
    var iterator = function(value) { return value.name; };
    deepEqual(_.map(_.uniq(list, false, iterator), iterator), ['moe', 'curly', 'larry'], 'can find the unique values of an array using a custom iterator');

    deepEqual(_.map(_.uniq(list, iterator), iterator), ['moe', 'curly', 'larry'], 'can find the unique values of an array using a custom iterator without specifying whether array is sorted');

    iterator = function(value) { return value +1; };
    list = [1, 2, 2, 3, 4, 4];
    deepEqual(_.uniq(list, true, iterator), [1, 2, 3, 4], 'iterator works with sorted array');

    var result = (function(){ return _.uniq(arguments); })(1, 2, 1, 3, 1, 4);
    deepEqual(result, [1, 2, 3, 4], 'works on an arguments object');

    deepEqual(_.uniq(null), []);

    var context = {};
    list = [3];
    _.uniq(list, function(value, index, array) {
      strictEqual(this, context);
      strictEqual(value, 3);
      strictEqual(index, 0);
    }, context);
  });

  describe('intersection', function() {
    var stooges = ['moe', 'curly', 'larry'], leaders = ['moe', 'groucho'];
    deepEqual(_.intersection(stooges, leaders), ['moe'], 'can take the set intersection of two arrays');
    deepEqual(_(stooges).intersection(leaders), ['moe'], 'can perform an OO-style intersection');
    var result = (function(){ return _.intersection(arguments, leaders); })('moe', 'curly', 'larry');
    deepEqual(result, ['moe'], 'works on an arguments object');
    var theSixStooges = ['moe', 'moe', 'curly', 'curly', 'larry', 'larry'];
    deepEqual(_.intersection(theSixStooges, leaders), ['moe'], 'returns a duplicate-free array');
    result = _.intersection([2, 4, 3, 1], [1, 2, 3]);
    deepEqual(result, [2, 3, 1], 'preserves order of first array');
    result = _.intersection(null, [1, 2, 3]);
    equal(Object.prototype.toString.call(result), '[object Array]', 'returns an empty array when passed null as first argument');
    equal(result.length, 0, 'returns an empty array when passed null as first argument');
    result = _.intersection([1, 2, 3], null);
    equal(Object.prototype.toString.call(result), '[object Array]', 'returns an empty array when passed null as argument beyond the first');
    equal(result.length, 0, 'returns an empty array when passed null as argument beyond the first');
  });

  describe('union', function() {
    var result = _.union([1, 2, 3], [2, 30, 1], [1, 40]);
    deepEqual(result, [1, 2, 3, 30, 40], 'takes the union of a list of arrays');

    result = _.union([1, 2, 3], [2, 30, 1], [1, 40, [1]]);
    deepEqual(result, [1, 2, 3, 30, 40, [1]], 'takes the union of a list of nested arrays');

    var args = null;
    (function(){ args = arguments; })(1, 2, 3);
    result = _.union(args, [2, 30, 1], [1, 40]);
    deepEqual(result, [1, 2, 3, 30, 40], 'takes the union of a list of arrays');

    result = _.union([1, 2, 3], 4);
//    deepEqual(result, [1, 2, 3], 'restrict the union to arrays only');
  });

  describe('difference', function() {
    var result = _.difference([1, 2, 3], [2, 30, 40]);
    deepEqual(result, [1, 3], 'takes the difference of two arrays');

    result = _.difference([1, 2, 3, 4], [2, 30, 40], [1, 11, 111]);
    deepEqual(result, [3, 4], 'takes the difference of three arrays');

    result = _.difference([1, 2, 3], 1);
//    deepEqual(result, [1, 2, 3], 'restrict the difference to arrays only');
  });

  describe('zip', function() {
    var names = ['moe', 'larry', 'curly'], ages = [30, 40, 50], leaders = [true];
    var stooges = _.zip(names, ages, leaders);
    equal(String(stooges), 'moe,30,true,larry,40,,curly,50,', 'zipped together arrays of different lengths');

    stooges = _.zip(['moe',30, 'stooge 1'],['larry',40, 'stooge 2'],['curly',50, 'stooge 3']);
    deepEqual(stooges, [['moe','larry','curly'],[30,40,50], ['stooge 1', 'stooge 2', 'stooge 3']], 'zipped pairs');

    // In the case of difference lengths of the tuples undefineds
    // should be used as placeholder
    stooges = _.zip(['moe',30],['larry',40],['curly',50, 'extra data']);
    deepEqual(stooges, [['moe','larry','curly'],[30,40,50], [undefined, undefined, 'extra data']], 'zipped pairs with empties');

    var empty = _.zip([]);
    deepEqual(empty, [], 'unzipped empty');
  });

  describe('object', function() {
    var result = _.object(['moe', 'larry', 'curly'], [30, 40, 50]);
    var shouldBe = {moe: 30, larry: 40, curly: 50};
    ok(_.isEqual(result, shouldBe), 'two arrays zipped together into an object');

    result = _.object([['one', 1], ['two', 2], ['three', 3]]);
    shouldBe = {one: 1, two: 2, three: 3};
    ok(_.isEqual(result, shouldBe), 'an array of pairs zipped together into an object');

    var stooges = {moe: 30, larry: 40, curly: 50};
    ok(_.isEqual(_.object(_.pairs(stooges)), stooges), 'an object converted to pairs and back to an object');

    ok(_.isEqual(_.object(null), {}), 'handles nulls');
  });

  describe('indexOf', function() {
    var numbers = [1, 2, 3];
    numbers.indexOf = null;
    equal(_.indexOf(numbers, 2), 1, 'can compute indexOf, even without the native function');
    var result = (function(){ return _.indexOf(arguments, 2); })(1, 2, 3);
    equal(result, 1, 'works on an arguments object');
    equal(_.indexOf(null, 2), -1, 'handles nulls properly');

    var num = 35;
    numbers = [10, 20, 30, 40, 50];
    var index = _.indexOf(numbers, num, true);
    equal(index, -1, '35 is not in the list');

    numbers = [10, 20, 30, 40, 50]; num = 40;
    index = _.indexOf(numbers, num, true);
    equal(index, 3, '40 is in the list');

    numbers = [1, 40, 40, 40, 40, 40, 40, 40, 50, 60, 70]; num = 40;
    index = _.indexOf(numbers, num, true);
    equal(index, 1, '40 is in the list');

    numbers = [1, 2, 3, 1, 2, 3, 1, 2, 3];
    index = _.indexOf(numbers, 2, 5);
    equal(index, 7, 'supports the fromIndex argument');

    index = _.indexOf([,,,], undefined);
//    equal(index, 0, 'treats sparse arrays as if they were dense');
  });

  describe('lastIndexOf', function() {
    var numbers = [1, 0, 1];
    equal(_.lastIndexOf(numbers, 1), 2);

    numbers = [1, 0, 1, 0, 0, 1, 0, 0, 0];
    numbers.lastIndexOf = null;
    equal(_.lastIndexOf(numbers, 1), 5, 'can compute lastIndexOf, even without the native function');
    equal(_.lastIndexOf(numbers, 0), 8, 'lastIndexOf the other element');
    var result = (function(){ return _.lastIndexOf(arguments, 1); })(1, 0, 1, 0, 0, 1, 0, 0, 0);
    equal(result, 5, 'works on an arguments object');
    equal(_.lastIndexOf(null, 2), -1, 'handles nulls properly');

    numbers = [1, 2, 3, 1, 2, 3, 1, 2, 3];
    var index = _.lastIndexOf(numbers, 2, 2);
    equal(index, 1, 'supports the fromIndex argument');
  });

  describe('range', function() {
    deepEqual(_.range(0), [], 'range with 0 as a first argument generates an empty array');
    deepEqual(_.range(4), [0, 1, 2, 3], 'range with a single positive argument generates an array of elements 0,1,2,...,n-1');
    deepEqual(_.range(5, 8), [5, 6, 7], 'range with two arguments a &amp; b, a&lt;b generates an array of elements a,a+1,a+2,...,b-2,b-1');
    deepEqual(_.range(8, 5), [8, 7, 6], 'range with two arguments a &amp; b, b&lt;a generates an empty array');
    deepEqual(_.range(3, 10, 3), [3, 6, 9], 'range with three arguments a &amp; b &amp; c, c &lt; b-a, a &lt; b generates an array of elements a,a+c,a+2c,...,b - (multiplier of a) &lt; c');
    deepEqual(_.range(3, 10, 15), [3], 'range with three arguments a &amp; b &amp; c, c &gt; b-a, a &lt; b generates an array with a single element, equal to a');
    deepEqual(_.range(12, 7, -2), [12, 10, 8], 'range with three arguments a &amp; b &amp; c, a &gt; b, c &lt; 0 generates an array of elements a,a-c,a-2c and ends with the number not less than b');
    deepEqual(_.range(0, -10, -1), [0, -1, -2, -3, -4, -5, -6, -7, -8, -9], 'final example in the Python docs');
  });
